Optical fiber communications experience degradation due to various physical properties of the optical fiber. Other network elements may also contribute to the degradation of the signal. This degradation tends to limit the distance over which information can be effectively communicated. For example, the propagation velocity of an optical signal within an optical fiber is wavelength dependent. Due to the spectral content of a pulse, the optical pulses tend to become spread out or broadened through a phenomenon referred to as material or chromatic dispersion.
Various compensation techniques have been developed to mitigate the effects of dispersion. Optical dispersion compensation modules (ODCMs) are sometimes used in an effort to compensate for unwanted chromatic dispersion. One type of ODCM utilizes spools of dispersion compensating fiber (DCF) to ameliorate the chromatic dispersion contributed by the primary optical fiber.
One disadvantage of this approach is the labor-intensive nature of determining and implementing the appropriate compensation. A technician must select the appropriate length DCF spool for the ODCM. Another disadvantage of such ODCMs is the need to rely on commercially available spools of pre-determined lengths of DCF rather than custom-length DCF. The granularity of commercially available spool lengths leads to less-than-optimal compensation.
Perhaps most importantly, changes to the amount of compensation inherently require the undesirable interruption of data transport. Changes require technician scheduling lead time and interruption of data transport to exchange DCF spools. The static nature of DCF compensation is also incapable of handling time-varying dispersion.